Aqueous aluminum salts are typically acidic and can form complex cations, anions, and molecules whose structure is dependent on pH, for example cations such as [Al13O4(OH)24(H2O)12]7+. Polyaluminum salts find application as flocculants and in water treatment and purification. Such aluminum compounds tend to contain group V, VI, and VII elements, as well as metals as contaminants. Halogen content such as chloride, for example, can limit the use of such compounds in applications where such content is undesirable. For example, if the aluminum compound is a component of a product that is subsequently subject at any point its life cycle to heating and/or combustion (e.g. incineration of the product after disposal), toxic gaseous byproducts containing chlorine may evolve. Therefore there is a need to prepare polyaluminum salts free of the presence of undesirable contaminating amounts of group V, VI, VII and other elements. Furthermore, there is a need to prepare aluminum compounds and compositions including aqueous aluminum compositions of high purity for applications that are impurity sensitive, for example if the aluminum compounds are used as or used in the synthesis of catalysts. One particular class of catalysts is zeolites.
Zeolites are microporous, metalosilicate composites or minerals, typically aluminosilicate composites are commonly used as commercial adsorbents and catalysts. While zeolites occur naturally, they are also produced industrially on a large scale. Zeolites are characterized as microporous because their constituent silicon, oxygen, and metal/aluminum atoms are arranged into various ring configurations which are positioned in a series such that the series of rings define channels passing through the mineral. The specific number and ratio of types of atoms in any given ring determines the width of the channels. As a result, different numbered rings can result in channel width which varies in order to accommodate only one or some of specific ions/cations such as Na+, K+, Ca2+, Mg2+, or others.
Because of their unique structure and their ion-specific affinity, zeolites possess a number of properties that are desirable for a wide range of industrial and commercial uses. As a result of these properties zeolites are often used as and referred to as molecular sieves. Uses include, but are not limited to, ion-exchange, water purification, water softening, catalysts, sorbents, gas separation, oxygen generation, petrochemical catalysts, Lewis acid catalysts, catalytic cracking catalysts, nuclear-radioactive materials, hygroscopic heat absorbers, detergents, asphalt-concrete substrates, gemstones, blood clotting agents, potassium releasing fertilizers, agricultural water releasing agents, and aquarium filters.